Noritz Tankless Water Heater Making Loud Noise [Reasons + Solutions]

The leading reasons behind your Noritz tankless water heater making loud noise are:

  • A dirty flow sensor.
  • Loose parts. 
  • Sediment build-up and restricted water flow.
  • Leakage
  • And, water pressure fluctuations.

Whatever the reasons, we have sorted them out with well-proven solutions.

noritz tankless water heater making loud noise

While you’re struggling to fix your heater noise issue, first check out the flow sensors and clean up the carbon buildup from there. Hopefully, you will get the solution. If it isn’t proving well, go on reading…

Table of Contents

Noritz Tankless Water Heater Making Loud Noise [Reasons + Solutions]

Here are the details of all the common reasons related to your Noritz tankless water heater creating loud noises and a guide on how to eliminate the problems. Let’s read between the lines.

Note: You can also read how to fix the noritz tankless water heater no display.

1. Dirty Flow Sensor

A dirty flow sensor is one of the major culprits for your tankless water heater generating loud noise.

Typically, Noritz water heater heat flows based on the spinning of the wheel of the flow sensor. Plus, the flow sensor detects the high or low flow flame, causing the water to turn into a stream in the unit. 

noritz tankless water heater flow sensor 

But when the sensor is bad, a vacuum siphons away from the unit and can’t read the flow momentarily. As a result, it produces a loud sound during the operation.

Again, if the gas controller loop can’t give feedback via the flame temperature sensor, you may hear a loud noise from this unit. Whatever the reasons, solve the problems by following tips.


The first thing is to identify the source of the noise. Check out the sensor if it has built up any dirt or damage. Let’s follow the tips:

Turn off the power and gas supply. Remove the outer 4 screws and locate the flow sensor. Next, pull out the flow sensor impeller and locate a plastic dome inside the short of the flow sensor. Disassemble the sensor and inspect whether the parts are set to the right position or blocked by dirt. 

After identifying any dirt, carefully clean the dirt like a plumber’s putty or flux from each of the little parts using a soft cloth so that they mayn’t be damaged.

After cleaning the part, push the sensor into the big cylinder units. Then, place and screw in the flow sensor’s parts to hold them in place. Next, put the flow sensor back on the heater and push the flow sensor down right into the bottom connection.

Finally, screw the parts as you had removed them first. Turn on the gas, and reconnect the electrical power to run the heater again. Slowly pressurize your heater. Hopefully, your flow sensor won’t be troublesome further. Even if any noise comes from your heater, don’t ignore checking out the sediment case in the heater.

2. Accumulation Of Sediment

Building up sediment is the next culprit for causing a loud noise in your water heater. A tankless water heater builds up minerals, especially if you are living in hard water areas.

Unfortunately, you will hear the below sounds if the sediment accumulates in your system. For instance:

  • Rambling– Normally builds up sediment in the system.
  • Popping– When the huge sediment starts to break from the heat.
  • Sizzling, Hissing & Crackling—sediment in the base of the tank.

Besides, this sediment may break the pipes and even can damage your beloved heater. If that happens, your heater will make a sound like a water hammer. However, you can operate a flush on your system by yourself to stop it from noising.


To remove sediment and reduce the noise from your heater, flush out your system with vinegar at least once a year to protect further problems. To do so, you will need the following things.

things are needed to remove the sediment
  • Grade White Vinegar (3-4) Gallons
  • 5- Gallon size Bucket
  • Submersible pump
  • 3-4″ Hose Drain Connections and screwdriver.

How To Remove Sediment

First, shut off the cold water valve. Turn the power off at the breaker and let it cool down completely. Then, attach the garden hose to the drain at the lower part of the tank and place the other at the end of the floor in a bucket outside the house. 

Second, open hot water faucets to protect a water vacuum. Next, open the drain valve and let the water pour out fully until the tank becomes empty. Now, release the supply line for at least 5 minutes to drain more sediment out. Repeat the process until clearing the whole sediment.

remove sediment

After That, remove the hose and insert a screwdriver to drain out the hardened particles and loosen the blockage debris. After removing the blockage, rejoin the hose and then continue to drain out the water. Keep off the valve and open the water inlet valve. Now, turn off the faucet whether the entrapped air is out of the line.

Yet, if the flushing system can’t solve the problem, add an arrester to the water system line to get rid of water hammering. Plus, you need to set up an automatic or manual air vent at the highest point of the waterline to avoid further problems.. After completing the steps successfully, reattach the units to their right place and turn on your heater.

Note: You can watch the velow video on how to flush out the sediment from your Noritz water heater.

3. Loose Parts

If there is no issue with the flow sensor or sediment, we bet the noise comes from the loose parts of your heater. This issue may occur if the pipe connections, heating elements, or any other parts become detached in-course of time.

noritz tankless water heater loose parts

Basically, your Noritz heater will make a noise like vibrating, humming, buzzing, and hammering  if:

  • The direction of the water flow changes suddenly.
  • It gets insufficient space for condensation.
  • Water is flowing under the heating element.

After all, the above issues loosen the heating elements and water supply lines. Whatever the case, here is the solution for you.


To resolve the losing issue, find out the source of the noise. After identifying any loose parts, take a proper wrench and socket and tighten them to prevent them from entering the flow of water. Plus, investigate if the heating element parts get loose. Because identifying the loose parts properly could save you from particular damage in the future. 

Next, we would suggest you recheck whether the water lines are secured in their right place, such as—copper for copper and metal for the metal pipe. 

In addition, consider installing a spacer pipe or hammer arrestor close to the valve to avoid intolerable noise. If the issue isn’t fixed yet, there might be trouble with water flow. 

4. Restricted Water Flow

Restricted water flow is another common reason for creating a loud noise with your water heater. When your tankless water heater sounds quietly irritating, screeching, or screaming, it is a sign that the water flow unit has been blocked in any way.

restricted water flow

The above sounds also hint that the flow of water has been restricted into or out of the heater. Besides, you will hear these sounds if the temperature pressure valve falls or becomes blocked because of creating excessive pressure.


To get random water flow, inspect whether the water flow is restricted. If it happens, release the excess pressure through the tank that causes the heater to make a noise.

Then, check that the inlet and outlet valves are fully open. Because a restricted valve can be closed that makes noise. When a restriction of water flow isn’t an issue, then the pressure release valve may be a cause for creating noise. So, try to keep the valve pressure limit within 50 psi by releasing extra pressure.

5. Pressure Valve Issues

An unpleasant ticking noise is coming from your tankless water heater when the water valve is opened low to medium. with 

Typically, your heater will make ticking noise because of an incorrect setting of pressure relief valves, the closing of the valves, and the abrupt fluctuation of water pressure.

pressure valve issues

Plus, your pressure release valve may malfunction and cause horrible vibration when the heater is in running mode if-

  • The venting is not assembled, which also causes combustion troubles.
  • The unit doesn’t have a pressure-reducing valve
  • It is set too high
  • There is a defective pressure valve 
  • And a faulty heat exchanger.


First, inspect if the inlet and outlet relief valves are fully opened. If not, rotate the valves until they are in the right position.

To reduce the vibration, first, remove the cover and locate the 4 buttons on the right side of the unit. You will find there are UP and DOWN buttons with Manifold Minimum and Manifold Maximum buttons. Set the minimum and maximum settings using the manifold button on the unit. We’ll recommend you start with the minimum setting first.

Then, turn the water valve ON to simulate the MIN pressure flow. Press the Up and Down buttons repeatedly until you set the pressure. Again, do the same thing with Maximum Button. 

After that, ensure the water valve is in a good position and the vent system is running properly. Notice, if the pressure-reducing valve is defective, replace it with a properly sized valve. Now, adjust all specifications to the point. 

Though the Noritz inlet pressure is 150 Psi, it doesn’t mean that you would operate with such high pressure. So, manually, the set point should be 50 Psi. Expectantly, the issue will be fixed.

But when your pressure valve is in good condition, the noise might come from leakage in the heater.

6. Issued With Leakage

Your water heater is running, but you are hearing a hissing sound. This is normal. But if the sound goes beyond the limit and there is no hot water, be sure the Noritz water heater leakage is a major culprit behind it. 

noritz tankless water heater leakage

In fact, moisture, such as water on the floor or shipping out under walls means that there is a leak in the water line. The issue is really a matter of concern that should be fixed ASAP.


To resolve the leaks, first turn off the cold water supply and shut off the electrical breaker. Now, check for leakage. If the sound is coming from the leak in the heater, attach a hose to the drain near the lower part of the tank, then drain the tank outside. 

If this issue isn’t solved yet, you can install a thermal expansion tank to prevent water backflow. When the problem isn’t repairable, it is best to change the leakage lines or tank with a new one.

7. Problems With Fans

Sometimes your heater may make an intolerable noise because of the clogged fan as it restricts the fresh air supply.

Typically, a water heater’s fan induces combustion air and even helps significantly increase the output of hot water when many fixtures are being used at a time. But if it is in the out-of-balance wobble, the blades of the fan scream.

Besides, the fan is knocking or scraping due to-

  • Dirty and debris logged on fan blades or the gas unit.
  • Insects or lizards stuck with the fan’s blade.
  • And set too high a water temperature level.


To make sure the fan is fit, check out first if there is no attack by lizards or insects. If so, clean around it as needed by using a brush and also brush under the burner plate to clean dirt and debris. 

Then, apply compressed air to remove the particles. Finally, ensure that your water heater isn’t making loud noises. If you can’t bring your heater back to its usual condition, call a professional to inspect what is wrong with the water heater.

Maintenance Of The Notitz Tankless Water Heater

Noritz is an energy-efficient and excellent investment to get an endless supply of on-demand hot water in your home. But you may have experienced some noise issues with your heater. However, periodic maintenance ensures that it will ultimately reduce loud noise and keep your heater fit.

maintenance of the notitz tankless water heater

Plus, periodically look into heating elements. If the system gets overheated, shut down the unit immediately and call a professional to inspect minutely and maintain it to bring back your heater in working condition. Because a tankless water heater lasts long if you maintain it correctly.


Why does my water heater still knock after flushing or draining?

Your water heater is knocking due to accumulated hard sediment even after flushing. Because the hardened chunk of pebble is too difficult to drain out. So, install an arrestor to get rid of this issue.

Is it normal to make a noise with a tankless water heater?

A tankless water heater will make a slight noise while heating water. But when the noise level crosses 90 decibels, that causes concern,

What is the best temperature setting to reduce loud noises?

The water temperature is typically set at 115- 125°F, but it can be reduced to 110°F. This setting will reduce noise by causing too high pressure and extend the life of your tank.

Final Words

Now, you have a better understanding of why your Noritz tankless water heater is making loud noises and what different sounds mean. 

Whatever the cause, follow our exclusive guide to resolve your water heater sound problems. Plus, keep your water heater under periodic maintenance as it will help your heater to work quietly and efficiently for years.

Still, if you struggle to fix your trouble, don’t be hopeless. Rather, leave a comment for us. We will come back to you ASAP.

About William

William is the founder of He has practical skills in fixing smoker & heating appliance issues. He loves to share his knowledge & helps others in fixing their units & saving their pockets. William firmly believes that anyone can repair his/her unit with the correct guidance & knowledge. More about us.

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